radio carpal joint

7/31/2019 Radio Carpal Joint

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Radio-carpal joint- Shruti Shah.


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Anatomy The radiocarpal joint is formed by the radius

and radioulnar disc triangularfibrocartilagecomplex [TFCC] proximally and by scaphoid,lunate, and triquetrum distally.

The proximal radiocarpal joint surface has asingle continuous biconcave curvature that islong and shallow side to side (frontal plane)

and shorter and sharper anteroposteriorly(sagittal plane).


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The proximal joint surface is composed of :

1. The lateral radial facet that articulates with thescaphoid

2. The medial radial facet that articulates withthe lunate.

3. The TFCC that articulates predominantly withthe triquetrum although it also has somecontact with the lunate in the neutral wrist.

The proximal carpal row is the distal surface ofthe radiocarpal joint.


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The proximal carpal row and ligamentstogether appear to present a single biconvex

joint surface that, unlike a rigid segment, can

change shape somewhat to accommodate tothe demands of space between the forearmand hand.


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TFCC

The TFCC consists of the radioulnar disc, aconnective tissue wedge, and thevariousfibrous attachments. The disc is afibrocartilaginous continuation of thearticularcartilage of the distal radius.

The disc is connected medially via two densefibrous connective tissue laminae.


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The upper lamina attaches to the ulnar headand ulnar styloid; the lowerlamina has

connections to the sheath of the extensor carpiulnaris and to the triquetrum, hamate, and thebase of the fifth metacarpal via fibres from theulnar collateral ligament.


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Ligaments The ligaments of the wrist complex are

devided into extrinsic and intrinsic ligaments.

The extrinsic ligaments are those that connectthe carpals to the radius or ulnar proximallyor to the metacarpals distally

The intrinsic ligaments are those thatinterconnect the carpals themselves and arealso known as intercarpal or interosseousligaments


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Volar Carpal Ligaments:

The composite ligament known as the volar

radiocarpal ligament has been described mostcommonly as having three distinct bands:

1. Radioscaphoid

2. Radiotriquetral

3. Radiocapitate The composite ulnocarpal ligament arises

from the TFCC and has been described ashaving bands attaching to the lunate which is

called ulnolunate and to the capitate eitherdirectly called Ulnocapitate or indirectly viaulnotriquetral and capitotriquetral ligaments.


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Dorsal carpal ligaments :

The ligament as a whole converges on thetriquetrum from the distal radius, withpossible attachments along the way to thelunate and lunotriquetral interosseousligament.

Other ligament is dorsal intercarpal ligamentthat courses horizontally from the triquetrumto the lunate, scaphoid, and trapezium.

The two dorsal ligaments together form ahorizontal V that contributes to radiocarpalstability.


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Muscles Six muscles have tendons crossing the volar

aspect of the wrist and, therefore, are capableof creating a wrist flexion movement. Theseare as follows :

1. Palmaris Longus (PL)

2. Flexor Carpi Radialis (FCR)

3. Flexor Carpi Ulnaris (FCU)

4. Flexor Digitorum Superficialis (FDS)5. Flexor Digitorum Profundus (FDP)

6. Flexor Pollicis Longus (FPL)


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The first three of these muscles are primary

wrist muscles. The last three areflexors of thedigits with secondary actions at the wrist. Allpass under theproximal flexor retinaculum ofthe wrist, except the palmaris longus

andflexor carpi ulnaris.

The tendons of nine muscles cross the dorsumof the wrist complex. Three of the nine

muscles are primary wrist muscles, whereasthe other six are finger and thumb musclesthat may act secondarily on the wrist.


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These muscles areas follows :

Extensor Carpi Radialis Longus (ECRL)

Exensor Carpi Radialis Brevis (ECRB) Extensor Carpi Ulnaris (ECU)

Extensor Digitorum Communis (EDC)

Extensor Indicis Proprius (EIP)

Extensor Digiti Minimi (EDM)

Extensor Pollicis Longus (EPL)

Extensor Pollicis Brevis (EPB)

Abductor Pollicis Longus (APL)

The tendons of all nine muscles pass under theextensor retinaculum.


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Movements of wristcomplex

Flexion / Extension of the Wrist:

1. The motion begins with wrist in full flexion.

2. Active extension is initiated at the distalcarpal row and the attached metacarpals bythe wrist extensor muscles attached to thosebones.

3. The distal carpals (capitate, hamate,

trapezium, and trapezoid) glide on therelatively fixed proximal bones (scaphoid,lunate, and triquetrum)


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4. Although the surface configurations of the

midcarpal joint are complex, the distal carpalrow effectively glides in the same directionsmotion of the hand.

5. When the wrist complex reaches neutral, the

ligaments spanning the capitate and scaphoiddraw the capitate and scaphoid together intoa close-packed position.

6. Continued extensor force now moves thecombined unit of the distal carpal row andthe scaphoid on the relatively fixed lunateand triquetrum.


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7. At approximately 45 of hyperextension ofthe wrist complex, the scapholunateinterosseous ligament brings the scaphoidand lunate into close-packed position.

8. This unites all the carpals and causes them tofunction as a single unit.

9. Wrist complex extension is completed as theproximal articular surface of the carpalsmove as a solid unit on the radius andradioulnar disc.

10. All ligaments become taut as full extension is

reached and the entire wrist complex isclose-packed.

Wrist motion from full extension to fullflexion occurs in reverse sequence.


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Thank you

radio carpal joint

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